Issue 5183 - Provide async interface for FileSystem

src/DefaultFileSystem.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 50 matching lines @@
 #else
   // POSIX systems: assume that file system encoding is UTF-8 and just use the
   // file paths as they are.
   std::string NormalizePath(const std::string& path)
   {
     return path;
   }
 #endif
 }
 
-std::shared_ptr<std::istream>
+IFileSystem::IOBuffer
 DefaultFileSystemSync::Read(const std::string& path) const
 {
-  std::shared_ptr<std::istream> result(new std::ifstream(NormalizePath(path).c_str()));
-  if (result->fail())
+  std::ifstream file(NormalizePath(path).c_str(), std::ios_base::binary);
+  if (file.fail())
     throw RuntimeErrorWithErrno("Failed to open " + path);
-  return result;
-}
-
+
+  file.seekg(0, std::ios_base::end);
+  auto dataSize = file.tellg();
+  file.seekg(0, std::ios_base::beg);
+
+  IFileSystem::IOBuffer data(dataSize);
+  file.read(reinterpret_cast<std::ifstream::char_type*>(data.data()),
+            data.size());
+  return data;
+}
 
 void DefaultFileSystemSync::Write(const std::string& path,
-                                  std::istream& data)
+                              const IFileSystem::IOBuffer& data)
 {
   std::ofstream file(NormalizePath(path).c_str(), std::ios_base::out | std::ios_base::binary);
-  file << Utils::Slurp(data);
+  file.write(reinterpret_cast<const std::ofstream::char_type*>(data.data()),
+             data.size());
 }
 
 void DefaultFileSystemSync::Move(const std::string& fromPath,
                                  const std::string& toPath)
 {
   if (rename(NormalizePath(fromPath).c_str(), NormalizePath(toPath).c_str()))
     throw RuntimeErrorWithErrno("Failed to move " + fromPath + " to " + toPath);
 }
 
 void DefaultFileSystemSync::Remove(const std::string& path)
@@ skipping 108 matching lines @@
 
 void DefaultFileSystem::Read(const std::string& path,
                              const ReadCallback& callback) const
 {
   auto impl = syncImpl;
   std::thread([impl, path, callback]
   {
     std::string error;
     try
     {
-      auto result = impl->Read(path);
-      std::stringstream output;
-      output << result->rdbuf();
-      std::string buffer = output.str();
-      callback(std::move(buffer), error);
+      auto data = impl->Read(path);
+      callback(std::move(data), error);
       return;
     }
     catch (std::exception& e)
     {
       error = e.what();
     }
     catch (...)
     {
       error =  "Unknown error while reading from " + path;
     }
-    callback(std::string(), error);
+    callback(IOBuffer(), error);
   }).detach();
 }
 
 void DefaultFileSystem::Write(const std::string& path,
-                              std::shared_ptr<std::istream> data,
+                              const IOBuffer& data,
                               const Callback& callback)
 {
   auto impl = syncImpl;
   std::thread([impl, path, data, callback]
   {
     std::string error;
     try
     {
-      impl->Write(path, *data);
+      impl->Write(path, data);
     }
     catch (std::exception& e)
     {
       error = e.what();
     }
     catch (...)
     {
       error = "Unknown error while writing to " + path;
     }
     callback(error);
@@ skipping 69 matching lines @@
       error = "Unknown error while calling stat on " + path;
     }
     callback(StatResult(), error);
   }).detach();
 }
 
 std::string DefaultFileSystem::Resolve(const std::string& path) const
 {
   return syncImpl->Resolve(path);
 }